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CHEMINFO Record Number: 794
CCOHS Chemical Name: Lactic Acid

1-Hydroxyethanecarboxylic acid
2-Hydroxypropanoic acid
2-Hydroxypropionic acid
alpha-Hydroxypropionic acid
DL-Lactic acid
Milk acid

Chemical Name French: Acide lactique
Chemical Name Spanish: Acido dl lactico
CAS Registry Number: 50-21-5
Other CAS Registry Number(s): 598-82-3 79-33-4 10326-41-7
RTECS Number(s): OD2800000
Chemical Family: Saturated aliphatic hydroxy carboxylic acid / saturated aliphatic hydroxy monocarboxylic acid / hydroxyalkanoic acid / propionic acid / hydroxypropionic acid
Molecular Formula: C3-H6-O3
Structural Formula: CH3-CH(OH)-C(=O)-OH


Appearance and Odour:
Commercial lactic acid is a colourless or slightly yellow viscous, odourless or almost odourless liquid.(1) Pure, anhydrous lactic acid is a white, odourless crystalline solid.(1,12,13) Hygroscopic (absorbs moisture from the air).

Odour Threshold:
9 mg/m3 (odor threshold concentration) (16)

Warning Properties:
Information not available for evaluation.

Lactic acid can exist in two chemical forms (isomers), D(-) lactic acid (CAS No. 10326-41-7), L(+) lactic acid (CAS No. 79-33-4). The commercial product is usually a mixture of the two forms, DL-lactic acid (CAS No. 598-82-3), which is typically available as the D(-) and L(+) lactic acids in a 1:1 ratio. Pure anhydrous lactic acid is a crystalline solid, but it is difficult to keep it in the pure anhydrous form because it is so hygroscopic. Therefore it is generally available as a solution in water, ranging from 22-90%.(1,3,12) Pure anhydrous lactic acid and its water solutions contain varying amounts of intermolecular esterification products, such lactoyllactic and polylactic acids.(13)

Uses and Occurrences:
Lactic acid is used mainly in food and food-related applications, for example as a food acidulant, flavouring agent, preservative, pickling agent, pH buffering agent, in the disinfection and packaging of meat, poultry and fish, and in the production of emulsifying agents used in foods. It is also used in cosmetic and pharmaceutical applications and formulations; in the manufacture of lactates, biodegradable lactic acid polymers and copolymers, paints and resins; plasticizer and catalyst for phenol-formaldehyde resins; in the leather tanning industry; in various textile-finishing operations and acid dyeing of wool; lithograph and textile printing developers; as an intermediate in duplicating ink manufacture and as a solvent in silk screen cleaning; in metal treatment as a biodegradable rust remover; pH adjustment of hardening baths for cellophane; solder flux; in adhesive formulations; in electroplating and electropolishing baths; detergent builders; in animal feeds; in agriculture for silage manufacture; and for the detection of glucose.(1,12,13)
Lactic acid is present in many foods, both naturally or as a product of microbial fermentation. L(+) Lactic acid is also a principal metabolic intermediate in most living organisms and occurs naturally in small quantities in the body(1,12)


Commercial lactic acid is a colourless or slightly yellow viscous, odourless or almost odourless. Pure, anhydrous lactic acid is a white, odourless, crystalline solid. Hygroscopic. May burn if strongly heated. CORROSIVE to the eyes. Can cause permanent eye damage, including blindness. SKIN IRRITANT. Causes severe skin irritation.


Effects of Short-Term (Acute) Exposure

Lactic acid does not readily form a vapour. Therefore, inhalation exposures are unlikely to occur unless solutions are heated or misted. The dust is very hygroscopic (absorbs moisture from the air) and is not expected become airborne. Based on its acidity, airborne lactic acid is expected to be irritating to the nose, throat and upper respiratory tract. No human or animal information was located.

Skin Contact:
Lactic acid solutions can cause severe skin irritation, based on animal information and pH. Effects are related to the concentration of the solution and the duration of exposure. More concentrated solutions or longer exposures will produce more severe effects. Mild to severe irritation has been observed in humans and animals.
Several tests have been conducted where cosmetics formulations containing low concentrations of lactic acid have been applied to the skin of volunteers. Irritation ranged from mild to severe.(1) In one study, volunteers were exposed to 88% pure lactic acid for up to 4 hours. No irritation was noted at 15 minutes to 1 hour, while 21/16 volunteers noted moderate to severe irritation from 2 to 4 hours.(2)

Eye Contact:
Lactic acid causes serious eye damage, based on animal information. Depending on the concentration of the solution and the degree of exposure, permanent eye damage, including blindness, could result. In animals, undiluted lactic acid caused serious eye damage while a 15% solution caused severe injury.

Lactic acid may cause severe irritation of the mouth, throat and stomach. Concentrated solutions could cause severe injury and possibly death. Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

SKIN SENSITIZATION: Negative results have been obtained in studies which have evaluated the sensitizing potential of cosmetic products containing lactic acid.(1)


There is no human information available. No firm conclusions can be drawn from the limited animal information available, but it is unlikely that lactic acid is carcinogenic.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has no listing for this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human information available.

Reproductive Toxicity:
There is no human information available.

There is no human information available. Mostly negative results have been obtained in bacteria and cultured mammalian cells. Positive results have been attributed to the effect of pH, rather than mutagenicity.

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
L(+) Lactic acid is a normal metabolic intermediate produced by most mammalian cells. Sources of lactic acid production within the body include muscular activity and liver and blood metabolism. It is absorbed from the gastrointestinal tract after oral administration. It is then converted to pyruvic acid, which can be metabolized further to carbon dioxide, converted to glucose or stored as glycogen. Carbon dioxide is eliminated in expired air.(1)


If symptoms are experienced, remove source of contamination or move victim to fresh air and obtain medical advice.

Skin Contact:
Avoid direct contact. Wear chemical protective clothing, if necessary. As quickly as possible, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Immediately flush with lukewarm, gently flowing water for 15-20 minutes. Immediately obtain medical attention. Completely decontaminate clothing, shoes and leather goods before re-use or discard.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 30 minutes, while holding the eyelid(s) open. If a contact lens is present, DO NOT delay irrigation or attempt to remove the lens until flushing is done. Neutral saline solution may be used as soon as it is available. DO NOT INTERRUPT FLUSHING. If necessary, continue flushing during transport to emergency care facility. Quickly transport victim to an emergency care facility.

NEVER give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Immediately obtain medical attention.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
Greater than 110 deg C (greater than 230 deg F) (closed cup) (commercial product).(14) It is reported to be combustible.(15)

Lower Flammable (Explosive) Limit (LFL/LEL):
Not available

Upper Flammable (Explosive) Limit (UFL/UEL):
Not available

Autoignition (Ignition) Temperature:
Not available

Sensitivity to Mechanical Impact:
Not sensitive. Stable material.

Sensitivity to Static Charge:
Lactic acid solutions will not accumulate static charge since they have very high electrical conductivities.(13) No specific information is available for the solid material. However, it is very hygroscopic and is not expected to present a dust explosion hazard.

Electrical Conductivity:
5.67 X 10(9) pS/m (88.6% solution); 1.53 X 10(11) pS/m (54.9%); 3.82 x 10(11) pS/m (25%); 3.67 X 10(11) pS/m (6.3%) (13)

Combustion and Thermal Decomposition Products:
Incomplete combustion may produce irritating fumes and acrid smoke.(14)

Fire Hazard Summary:
Lactic acid may burn if strongly heated. During a fire, irritating/toxic gases and fumes may be generated.

Extinguishing Media:
Carbon dioxide, dry chemical powder, alcohol foam, polymer foam or water spray or fog.(14)

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind to avoid possible toxic decomposition products.
Water or foam may cause frothing. The frothing may be violent and could endanger personnel close to the fire. However, a water spray or fog that is carefully applied to the surface of the burning material, preferably with a fine spray or fog nozzle, will cause frothing that will blanket and extinguish the fire. In addition, water spray or fog can be used to prevent dust formation, absorb heat, keep containers cool and protect exposed material. If a leak or spill has not ignited, use water spray to disperse the vapours and protect personnel attempting to stop a leak. Water spray may be used to flush spills away from ignition sources. Solid streams of water may be ineffective and spread material.
Lactic acid is hazardous to health. Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker gear) will not provide adequate protection. Chemical protective clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 90.08

Conversion Factor:
1 ppm = 3.677 mg/m3; 1 mg/m3 = 0.272 ppm at 25 deg C (calculated)

Physical State: Liquid
Melting Point: 16.8 deg C (62.2 deg F) (DL-lactic acid racemic mixture); 53 deg C (61.4 deg F) (D- or L-lactic acid) (1,12,13)
Boiling Point: 125-140 deg C (257-284 deg F) at 27 kPa (form not specified) (13); 103 deg C (217.4 deg F) at 0.27 kPa (D- or L-lactic acid) (1)
Relative Density (Specific Gravity): 1.201 (88.6% solution); 1.13 (54.9%) (1); 1.057 (25%) at 25 deg C (13); 1.224 at 20 deg C (solid) (12) (water = 1)
Solubility in Water: Completely soluble (1,13)
Solubility in Other Liquids: Completely soluble in ethanol, diethyl ether, acetone, glycerol and other organic solvents which are miscible with water. Practically insoluble in benzene, chloroform ,and petroleum ether.(1,13)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = -0.62 (17); log P(oct) = -0.72 (3)
pH Value: Less than 1 (concentrated acid); 2.28 (1% solution); 1.75 (10%) (1,13)
Acidity: Moderately strong acid: pKa = 3.86 at 25 deg C (Ka = 1.38 X 10(- 4) at 25 deg C (1,12,13)
Viscosity-Dynamic: 36.9 mPa.s (36.9 centipoise) (88.6% solution) (12,13); 4.68 mPa.s (4.68 centipoise) (54.9%); 1.725 mPa.s (1.725 centipoise) (25%) at 25 deg C (13)
Viscosity-Kinematic: 30.73 mm2/s (30.73 centistokes) (88.6%); 4.14 mm2/s (4.14 centistokes) (54.9%); 1.63 mm2/s (1.63 centistokes) (25%) at 25 deg C (calculated)
Vapour Density: Not available
Vapour Pressure: 0.011 kPa (0.0813 mm Hg) at 25 deg C (calculated) (3)
Saturation Vapour Concentration: 107 ppm (0.011%) (calculated)
Evaporation Rate: Not available; probably negligible.

Other Physical Properties:
ELECTRICAL CONDUCTIVITY: 5.67 X 10(9) pS/m (88.6% solution); 1.53 X 10(11) pS/m (54.9%); 3.82 x 10(11) pS/m (25%); 3.67 X 10(11) pS/m (6.3%) (13)


Not stable. Self-polymerizes, but does not form more hazardous chemicals.(1,12,13)

Hazardous Polymerization:
Does not occur.

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

STRONG OXIDIZING AGENTS (e.g. hydrogen peroxide, potassium permanganate, or chromates), STRONG ACIDS (e.g. sulfuric or nitric acids), BASES (e.g. sodium or potassium hydroxide), or REDUCING AGENTS (e.g. hydrogen iodide, lithium aluminum hydride or sodium borohydride) - may react vigorously or violently.(14,19)
NITRIC ACID and HYDROFLUORIC ACID - a mixture of the three acids is unstable and can react vigorously, reaching a temperature of 90 deg C, with vigorous gas evolution after about 12 hours.(1,18)

Hazardous Decomposition Products:
None reported

Conditions to Avoid:
Heat, open flames.

Corrosivity to Metals:
Corrosive to gray cast iron, steel, brass, nickel and lead at normal temperatures. Corrosive to aluminum and nickel-copper alloys above 38 deg C, and copper and bronze above 93 deg C. Not corrosive to aluminum at normal temperatures. Dilute solutions are not corrosive to types 304 and 316 stainless steels, but solutions greater than 80% may corrode these stainless steels. Not corrosive to titanium, gold, platinum, tantalum and zirconium.(20)


LD50 (oral, rat): 3730 mg/kg (4)
LD50 (oral, mouse): 4875 mg/kg (1,5 unconfirmed)
LD50 (oral, guinea pig): 1810 mg/kg (4)

LD50 (dermal, rabbit): Greater than 2000 mg/kg (5)

Eye Irritation:

Lactic acid has caused serious eye damage.

Application of 0.1 mL of 88% lactic acid for 1 minute caused corrosive injury to the eyes in 6 rabbits.(24) Application of 0.005 mL of a 15% solution produced severe injury in rabbits (scored over 5.0 where 5.0 is severe injury, including necrosis; graded 8/10).(6) Significant irritation was produced in rabbits following application of 10 and 20% solutions. The damage was reversible within 7 days, but only for the 10% dilution.(7) If allowed to remain on the eyes, both the undiluted acid and a 50% water solution have caused corneal tissue death and scarring in rabbit eyes.(8)

Skin Irritation:

Lactic acid is a severe skin irritant.

Application of 0.5 mL undiluted lactic acid to intact skin for 24 hours caused severe irritation in rabbits. Average scores for 24, 48 and 72 hours for each of 6 rabbits ranged from 3-4/4 for redness and from 1-2.3/4 for edema. The skin was shed after 10-14 days, but there was no in-depth injury.(24) Covered application of a 20% solution produced slight irritation in rabbits.(7) Application of 5 mg for 24 hours in a Standard Draize Test produced severe irritation in rabbits.(5, unconfirmed) Repeated application of 2 mL of undiluted lactic acid produced a severe intolerance in rabbits and dosing was discontinued after 1 week.(7)

Effects of Short-Term (Acute) Exposure:

Male rats were orally administered 130, 650 or 1300 mg/200 kg body weight of lactic acid. Within 24 hours, 2/5 animals administered 1300 mg and 1/5 animals administered 650 mg died. Following a second dosing 8 days later, 2 rats in the 1300 mg group died. Difficulty breathing, runny noses and vomiting were observed immediately after dosing.(9)

Effects of Long-Term (Chronic) Exposure:

Skin Contact:
Harmful effects were not observed in rats dermally exposed to a cosmetic product which contained a small amount of lactic acid for 13 weeks.(1)

No ill effects were observed in 2 dogs given 600-1600 mg/kg lactic acid orally 42 times over 2.5 months. Other studies involving rats, pigs and hamsters have also shown no effects following long-term oral administration.(1)

Skin Sensitization:
Lactic acid has produced negative results in a guinea pig maximization test.(1)

No tumours were reported in a limited study which examined the potential carcinogenicity of lactic acid in female rabbits exposed to 100 to 700 mg/kg orally for 5 or 16 months.(1, unconfirmed) No firm conclusions can be drawn from this study because of limitations such as the short duration.

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
One study has shown that lactic acid can produce mild fetotoxicity in the presence of maternal toxicity. Mice were orally exposed to 570 mg/kg on days 6-15 of pregnancy. Maternal toxicity, as evidence by decreased food consumption and decreased liver weight, was observed. Fetotoxicity (decreased bone ossification) was noted.(10)


Selected Bibliography:
(1) Final report on the safety assessment of glycolic acid, ammonium, calcium, potassium, and sodium glycolates, methyl, ethyl, propyl, and butyl glycolates, and lactic acid, ammonium, calcium, potassium, sodium, and TEA- lactates, methyl, ethyl, isopropyl, and butyl lacates, and lauryl, myristyl, and cetyl lactates. International Journal of Toxicology. Thirty-fourth report of the Cosmetic Review Expert Panel. Vol. 17, suppl. 1 (1998). p. 1-241
(2) York, M., et al. Evaluation of a human patch test for the identification and classification of skin irritation potential. Contact Dermatitis. Vol. 34, no. 3 (Mar. 1996). p. 204-212
(3) HSDB database record for lactic acid. Last revision date: 98/06/02
(4) Smyth, H.F., Jr., et al. The single dose toxicity of some glycols and derivatives. Journal of Industrial Hygiene and Toxicology. Vol. 23, no. 6 (June 1941). p. 259-268
(5) RTECS database record for lactic acid. Last updated: 1997-12.
(6) Carpenter, C.P., et al. Chemical burns of the rabbit cornea. American Journal of Ophthalmology. Vol. 29 (1946). p. 1363-1372
(7) Guillot, J.P., et al. Safety evaluation of some humectants and moisturizers used in cosmetic formulations. International Journal of Cosmetic Science. Vol. 4 (1982). p. 67-80
(8) Grant, W.M., et al. Toxicology of the Eye. 4th ed. Charles C. Thomas, 1993. p. 879-880
(9) Morotomi, M., et al. Effect and fate of orally administered lactic acid in rats. Journal of Nutritional Science and Vitaminology. Vol. 27, no. 2 (1981). p. 117-128
(10) Colomina, M.T., et al. Concurrent ingestion of lactate and aluminum can result in developmental toxicity in mice. Research Communications in Chemical Pathology and Pharmacology. Vol. 77, no. 1 (July 1992). p. 95-106
(11) Morita, T., et al. Evaluation of clastogenicity of formic acid, acetic acid and lactic acid on cultured mammalian cells. Mutation Research. Vol. 240, no. 3 (Mar. 1990). p. 195-202
(12) Datta, R. Hydroxycarboxylic acids: lactic acid. In: Kirk-Othmer encyclopedia of chemical technology. 4th ed. Vol. 13. John Wiley and Sons, 1995. p. 1042-1054
(13) Chahal, S.P. Lactic acid. In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised ed. Vol. A 15. VCH Verlagsgesellschaft, 1990. p. 97-105
(14) The Sigma-Aldrich library of chemical safety data. Ed. II. Vol. 1. Sigma-Aldrich Corporation, 1988. p. 2060D, 2061A,C,D
(15) Chemical safety sheets: working safely with hazardous chemicals. Kluwer Academic Publishers, 1991. p. 519
(16) Verschueren, K. Handbook of environmental data on organic chemicals. 3rd ed. Van Nostrand Reinhold, 1996. p. 1189-1190
(17) Leo, A., et al. Partition coefficients and their uses. Chemical Reviews. Vol. 17, no. 6 (Dec. 1971). p. 560
(18) Urben, P.G., ed. Bretherick's handbook of reactive chemical hazards. 5th ed. Vol. 2. Butterworth-Heinemann Ltd., 1995. p. 447, 1484
(19) Pohanish, R.P., et al. Rapid guide to chemical incompatibilities. Van Nostrand Reinhold, 1997. p. 476
(20) Corrosion data survey: metals section. 6th ed. National Association of Corrosion Engineers, 1985. p. 76-1 to 77-1
(21) Association of Official Analytical Chemists. Official Methods of Analysis. 15th ed. and Supplements. Washington, DC: Association of Analytical Chemists, 1990.
(22) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(23) DL-Lactic Acid . The Merck index: an encyclopedia of chemicals, drugs and biologicals. Edited by M.J. O'Neil, et al. 13th ed. Merck and Company, 2001. p. 955
(24) Younger Laboratories. Initial submission: toxicological investigation of: lactic acid with cover letter dated 081392. Date produced: Nov. 30, 1976. Monsanto Co. EPA/OTS 88-920007966. NTIS/OTS0570580.

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 2000-07-03

Revision Indicators:
Resistance of materials for PPE 2004-04-08
Composition/purity 2005-10-14
Melting point 2005-10-14
Bibliography 2006-01-12
Toxicological info 2006-01-25
Short-term eye contact 2006-01-25
Short-term skin contact 2006-01-25
Emergency overview 2006-01-25
First aid skin 2006-01-25
First aid eye 2006-01-25
First aid ingestion 2006-01-25
Handling 2006-01-26

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